U.S. Pat. No. 4,367,370, owned by the assignee of this application, discloses a wall system formed from a plurality of series-connected electrically prewired panels, and more specifically to a wall system wherein power-taps such as for light fixtures and conventional electrical receptacles can be selectively positioned on the panels and selectively switchably connected, at their point of use, to any one of a plurality of different electrical circuits. The wall system of the aforesaid panel is provided with a five-wire electrical system (three live, one neutral, and one ground wire) which defines three different electrical circuits extending along the wall system. A switchable power-tap is removably connected to a power block or terminal associated with the panels to permit circuit selection at the point of use. The power-tap is provided with a plug-in connection for engagement with the power block or terminal. Irrespective of which circuit the power-tap is connected to, however, the power-tap always connects to the same "neutral" wire since the power-tap permits selection only between the three different "live" wires.
The electrified wall system of the aforesaid patent, and specifically the switchable power-tap associated therewith, has proven highly desirable in its ability to permit a circuit-selecting function to be performed at each individual point of use. However, in a continuing effort to improve upon the design, simplicity, function, performance and reliability of the electrical system and of the power-taps associated therewith, specifically when the power-tap comprises a receptacle unit, the improved electrical system and circuit-selectable power-tap of this invention has been developed.
More specifically, this invention relates to an improved electrical system for a wall system formed from interconnected prewired wall panels, which electrical system is a seven-wire system formed by three live, three neutral and one ground wires. Each of the three circuits as defined by a respective one of the "live" wires has a dedicated "neutral". This thus significantly minimizes the noise or intermittent current as transmitted over the "neutral", such as due to phase shifting caused by inductive loads when several circuits share a common neutral, and hence makes the system more desirable for use with sensitive equipment such as computers and the like.
In the improved electrical system of this invention, there is provided an improved circuit-selectable power-tap which permits selection of any one of the three available circuits directly at the point of use, namely at the point of connection of the power-tap to the power block. The power-tap, which in a preferred form comprises a conventional receptacle unit, is provided solely with three contacts as prongs which create a plug-in type connection with the respective panel-mounted power block. These three contacts, as is conventional, constitute the "hot", "neutral" and "ground". However, the "hot" and "neutral" contacts, while being electrically isolated from one another, are mounted on a common insulative carrier which itself is movably, preferably slidably, mounted on the power-tap housing. This carrier and the "hot" and "neutral" contacts mounted thereon can hence be manually slidably displaced into three discrete positions which correspond to the three circuits defined in the power block. The carrier can be movably displaced only when the power-tap is disconnected from the power block. By initially positioning the carrier in one of the three available positions, the "live" and "neutral" contacts of the power-tap can be electrically engaged with any one of the selected circuits associated with the power block.